Engine covers of outboard motors include upper and lower cover members covering upper and lower halves of outboard motors. The upper and lower cover members are releasable from each other for the purpose of maintenance or adjustment of the engines. Seal members are interposed between the upper and lower cover members for sealing gaps between the upper and lower cover members.
The above type of seal members are known, for example, JP-U-63-89397 and JP-A-02-292575. JP-U-63-89397 discloses two seal members. The first one is an inverted-U-shaped water-proof member covering an erected lug formed at an outer peripheral edge of an upper part of a lower cover member. The second one is a water-proof member is located inside the first seal member and fitted into a hole formed on the upper part of the lower cover member. Since the number of the seal members for the lower cover member is two, the number of components of an outboard motor is greater and thus the number of steps for assembling an outboard motor is also greater. As a result, the cost for the outboard motor is higher.
JP-A-02-292575 discloses a seal member including a U-shaped base portion, a side lip projecting outwardly from outer side of the base portion, and a main lip projecting from a lower end of the base portion. The base portion of the seal member is fitted with an attachment rib projecting downwardly from a lower end of an inner peripheral edge of an upper cover member. The side lip abuts on an upper end of an outer periphery of a lower cover member when the upper cover member is attached to the lower cover member. The main lip is hollow and has a ring-shape. The main lip abuts on an upper end of an inner periphery of the lower cover member so as to seal a gap between the upper and lower cover members when the upper and lower cover members are attached to each other.
The main lip provides a watertight seal between the upper and lower cover members and, due to its hollow structure or ring-shape, has a reduced resiliency. Therefore, the main lip can not readily resume its original shape when undergoing plastic deformation. As a result, a reduced load is applied from the upper cover member to the lower cover member when the upper cover member is locked to the lower cover member. Where the ring-shaped main lip is compressed into a flattened state when the upper cover member is locked to the lower cover member, the height set on the basis of resilient force of the main lip can not be maintained. In this case, this main lip height should be maintained by additional means. However, such use of additional means leads to more complex structure or higher cost of the upper and lower cover members.
The reduced load on the lower cover member adversely affects sealing between the upper and lower cover members. Further, with the reduced load applied to the lower cover member, the upper cover member can be less reliably locked to the lower cover member.